This paper reviews findings on the anisotropy of the grain boundary energies. After introducing the basic concepts, there is a discussion of fundamental models used to understand and predict grain ...boundary energy anisotropy. Experimental methods for measuring the grain boundary energy anisotropy, all of which involve application of the Herring equation, are then briefly described. The next section reviews and compares the results of measurements and model calculations with the goal of identifying generally applicable characteristics. This is followed by a brief discussion of the role of grain boundary energies in nucleating discontinuous transitions in grain boundary structure and chemistry, known as complexion transitions. The review ends with some questions to be addressed by future research and a summary of what is known about grain boundary energy anisotropy.
Recrystallization and Related Annealing Phenomena fulfils the information needs of materials scientists in both industry and academia. The subjects treated in the book are all active research areas, ...forming a major part of at least four regular international conference series. This new third edition ensures the reader has access to the latest findings, essential to those working at the forefront of research in universities and laboratories. For those in industry, the book highlights applications of the research and technologically important examples. In particular, the third edition builds on the significant progress made recently in the following key areas:. Deformed state, including deformation to very large strains. Characterisation of microstructures by electron backscatter diffraction (EBSD). Modelling and simulation of annealing. . Continuous recrystallization.
50% revised and up-to-date, the 3rd edition highlights the significant recent literature results in grain growth in non-crystallizing systems; 3D characterization techniques; Quantitative modeling techniques, with all-new appendices on Texture and Measurements Synthesized, detailed coverage from leading authors bridges the gap between theory and practice by examining the application of quantitative, physically based models to metal forming processes Critical level of synthesis and pedagogy with an authored rather than edited volume
The transformation texture was studied in a Ti-6Al-4V alloy for two microstructures produced through different phase transformation mechanisms (i.e. diffusional vs. displacive). Both microstructures ...revealed qualitatively similar crystallographic texture characteristics, having two main texture components with Euler angles of (90 degree ,90 degree ,0 degree ) and (90 degree ,30 degree ,0 degree ). However, the overall alpha texture strength was considerably weaker in the martensitic structure (i.e. displacive mechanism) compared with the alpha + beta microstructure produced through slow cooling (i.e. diffusional mechanism). The intervariant boundary distribution in martensite mostly revealed five misorientations associated with the Burgers orientation relationship. The five-parameter boundary analysis also showed a very strong interface plane orientation texture, with interfaces terminated mostly on the prismatic planes {hki0}, when misorientation was ignored. The highest intervariant boundary populations belonged to the 63.26 degree / and 60 degree / misorientations, with length fractions of 0.38 and 0.3, respectively. The former was terminated on (), and the latter was a symmetric tilt boundary, terminated on (). The intervariant plane distribution in martensite was determined more by the constraints of the phase transformation than by the relative interface energies.
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•Possible grain boundary energy versus temperature phenomena are reviewed.•Grain boundary energy measurements are reviewed.•Relationships among the grain boundary energy, character, ...and complexion are reviewed.•The importance of future studies of complexion transition kinetics is stressed.
Recent findings about the role of the grain boundary energy in complexion transitions are reviewed. Grain boundary energy distributions are most commonly evaluated using measurements of grain boundary thermal grooves. The measurements demonstrate that when a stable high temperature complexion co-exists with a metastable low temperature complexion, the stable complexion has a lower energy. It has also been found that the changes in the grain boundary energy lead to changes in the grain boundary character distribution. Finally, recent experimental observations are consistent with the theoretical prediction that higher energy grain boundaries transform at lower temperatures than relatively lower energy grain boundaries. To better control microstructures developed through grain growth, it is necessary to learn more about the mechanism and kinetics of complexion transitions.
The relative grain boundary area and energy distributions of a ferritic steel were characterized as a function of lattice misorientation and boundary plane orientation using focused ion beam serial ...sectioning combined with electron backscatter diffraction. The grain boundary energy and population depended on both the grain boundary plane orientation and lattice misorientation. When misorientation was ignored grain boundary planes with the (111) orientation had the minimum energy and the largest relative areas. The most commonly observed boundaries were {112} symmetric tilt boundaries with the Σ3 misorientation; this boundary also had a low energy. On average there was a strong inverse correlation between the relative areas of different types of grain boundaries and the relative grain boundary energies.
Recently developed techniques to measure the structure of interfacial networks in three dimensions have the potential to revolutionize our ability to control the microstructures of polycrystals and ...interface‐dominated materials properties. This paper reviews recent findings from two‐ and three‐dimensional orientation mapping studies. The observations confirm a strong inverse correlation between the relative energies of grain boundaries and the frequency with which they occur in microstructures. The observations also show that during microstructure evolution, relatively higher energy grain boundaries are more likely to be shrinking while lower energy interfaces are more likely to be growing. These processes can lead to a steady‐state distribution of grain boundaries that is influenced as much by the relative grain‐boundary energies as by the exact processing conditions. Recent findings and emerging opportunities for grain‐boundary characterization are reviewed in the final section of the paper.
The properties of materials change, sometimes catastrophically, as alloying elements and impurities accumulate preferentially at grain boundaries. Studies of bicrystals show that regular atomic ...patterns often arise as a result of this solute segregation at high-symmetry boundaries, but it is not known whether superstructures exist at general grain boundaries in polycrystals. In bismuth-doped polycrystalline nickel, we found that ordered, segregation-induced grain boundary superstructures occur at randomly selected general grain boundaries, and that these reconstructions are driven by the orientation of the terminating grain surfaces rather than by lattice matching between grains. This discovery shows that adsorbate-induced superstructures are not limited to special grain boundaries but may exist at a variety of general grain boundaries, and hence they can affect the performance of polycrystalline engineering alloys.
The purpose of this paper is to describe the five-parameter grain boundary character distribution (GBCD) of polycrystalline silicon and compare it to distributions measured in metals and ceramics. ...The GBCD was determined from the stereological analysis of electron backscatter diffraction maps. The distribution of grain boundary disorientations is non-random and has peaks at 36°, 39°, 45°, 51°, and 60°. The axis-angle distribution reveals that most of the grain boundaries have misorientations around the 111, 110, and 100 axes. The most common grain boundary type (30 % number fraction) has a 60° misorientation around 111 and of these boundaries, the majority are twist boundaries. For other common boundaries, symmetric tilt configurations are preferred. The grain boundary character distribution of Si is distinct from those previously observed for metals and ceramics. The measured grain boundary populations are inversely correlated to calculated grain boundary energies available in the literature.
The intervariant boundary characteristics of a commercially pure Ti microstructure formed by the β→α martensitic phase transformation were described according to the crystallography of the displacive ...transformation and the boundary plane orientation. The martensitic transformation created a microstructure whose grain boundary misorientation angle distribution had four distinct peaks that were consistent with the misorientations between the variants produced by the Burgers orientation relationship. Interestingly, about 60% of population corresponded to 60°/112¯0 intervariant boundaries. Three-variant clusters with a triangular morphology were observed frequently. This configuration is consistent with the phenomenological theory of martensite, which predicts that these clusters, separated by 60°/112¯0 boundaries, have a lower transformation strain than other possible variant cluster arrangements. Other intervariant boundaries resulted from the impingement of different combinations of distinct three-variant clusters. The five-parameter boundary analysis revealed a strong anisotropy in the plane orientation distribution, showing that boundaries have a tendency to terminate on prismatic {hki0} and pyramidal {101¯1} planes, when misorientation was ignored. The dominant 60°/112¯0 intervariant boundaries had symmetric tilt (1¯101) boundary planes, which are a low energy configuration.
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